For a wireless communication system, one of most significant issues is spectrum scarcity because of limited radio frequency spectrum. With the evolution of LTE, the required bandwidth increases. To solve spectrum scarcity on LTE band and spectrum under-utilization on some other licensed band, it needs to deploy a cognitive LTE Network to opportunistically use spectrum holes, optimize the LTE system, and to enable it with CR technology.
In order to increase sensing-based incumbent detection reliability, new techniques to address the sensing coordination in heterogeneous scenarios are needed. Some problems when detecting heterogeneous primary system or secondary networks include: different channel bandwidth definitions by each of the coexisting networks, transmission signal power variations among operating standards, and signal characteristics among heterogeneous PHY modes.
For cognitive radio systems, a spectrum authorization scheme named “Authorized Shared Access (ASA)” is proposed. ASA is an evolutionary spectrum authorization scheme for sustainable economic growth and consumer benefit. ASA is a new spectrum management tool, using cognitive radio technologies, which permits controlled sharing of under-used spectrum. ASA enables timely availability and licensed use of harmonized spectrum for mobile with predictable quality of service. Alongside the use by the incumbent, a secondary user, the ASA user, can be granted an ASA right to utilize the under-used spectrum without interfering with the incumbent user. There may be one or several ASA users per frequency band as there may be one or several incumbent users. As a result, the ASA is an important contributor to solving the spectrum shortage.
Coordinated multipoint (CoMP) is a technology to minimize inter-cell interference. A plurality of geographically contiguous cells—referred to as constitute cells—are grouped together to form a CoMP cooperating set or a CoMP set. Each CoMP set has a serving node that coordinates transmission within its constituent sub-cells so as to minimize inter-cell interference within the CoMP cell (referred to herein as inter-sub-cell interference). The serving node minimizes inter-sub-cell interference by coordinating scheduling of transmissions to and from user equipment (UE) within the cells, and/or actively suppressing interference using signal processing techniques.
In a communication system employing both the ASA scheme and the CoMP scheme, when a primary system requests for the ASA frequency band (e.g., f1) in a specific area (protected area), an ASA controller sends a message including, for example, primary system's interference boundary, usage of spectrum and tolerable interference threshold to an operator OAM. The operator OAM forwards the message to a MME and requests the MME to evacuate the ASA spectrum f1 in areas that cause interference to the primary system. Upon receiving the message, the MME finds that a cell in the CoMP set will be affected. Then the MME requests a BS managing the cell (called as “affected BS”) to evacuate ASA spectrum f1. Therefore, the CoMP set will be changed due to ASA spectrum availability.
According to the conventional CoMP scheme, when the affected BS evacuates the ASA spectrum f1, the serving node does not immediately know CoMP set change, e.g., before the UE reports the loss of this specific cooperating cell. As such, the serving node can not determine whether the CoMP reception will be continued as expected in advance. As a result, the UE's QoS can not be ensured. Moreover, the serving node may still configure the UE to perform CoMP-related measurement even though the affected BS has evacuated the ASA spectrum f1.
As such, in the case that the CoMP set is changed due to the ASA spectrum change, the conventional scheme will introduce unnecessary signaling overhead and UE's measurement.
In view of the foregoing problem, there is a need to design a solution for managing a CoMP set in a communication system employing the ASA scheme, so as to reduce signaling reporting overhead, reduce UE's measurement and ensure continued execution of CoMP when the ASA spectrum utilization changes.